included in draft--08

The error codes have been added and checked into CVS.
 I think we need a general issue to
go over each operation's error list.

There are several sessions-related errors that need to be added to all or almost
all ops.  This is what I know about.  It may not be an exhaustive list.

First of all, the sequencing constraints means that any op (except for
CREATE_CLIENTID and CREATE_SESSION) cannot be the first op in a COMPOUND and so
all these ops need to have an appropriate sequencing error added to their error
lists.

Since a seesion can become invalid at any time and COMPOUND's are not atomic, I
think it has to be the case that every op (except the few that don't need a
session) has to be able to return a badsession error.  The fact that in most
implementations, this will only happen when the connection is also down does not
invalidate this need.